A fastener driving tool for driving fasteners, such as nails, drive screws, is a tool in which a connected fastener assembly formed of multiple connected fasteners is stored in a magazine and used so that the fasteners are driven continuously into workpieces.
Conventionally, as the connection configuration of the above-mentioned connected fastener assembly, for example, a straight type in which the fasteners are connected straight, a type in which the fasteners are connected and formed into a step-like shape and a coil type in which the fasteners are connected and wound into a coil are known.
Moreover, fasteners used to anchor wood to wood, to fasten liners or wood to concrete, to secure I-beams to thin steel sheets and to fasten denz glass (a plaster board-like material) to studs are usually connected to one another and loaded into a fastener driving tool. As methods for connecting fasteners to form a connected fastener assembly, various methods are known: for example, a stick type connecting method in which multiple fasteners are integrally connected to a straight connecting band made of a synthetic resin, a wire connecting method in which the shaft sections of fasteners are connected using two parallel metal wires by welding, and the so-called plastic sheet connecting method in which retaining pieces provided at constant intervals are bent in the same direction so as to protrude from the upper and lower ends of a connecting band made of a synthetic resin and having a thin sheet shape and fasteners are inserted into the upper and lower retaining pieces. As an example of the synthetic resin connecting method, the method disclosed in Patent documents 1 and 4 are known. In addition, as an example of the plastic sheet connecting method, the method disclosed in Patent documents 2 and 5 are known. Furthermore, a method in which fasteners are connected using a connecting sheet made of a synthetic resin is also known. This connecting sheet comprises shaft guides for allowing the shaft sections of fasteners to be passed through and retained and connecting sections for connecting adjacent shaft guides (refer to Patent documents 6 and 7).
Furthermore, as fastener connecting means, connecting means having a configuration in which the upper and lower portions of a carrier having a complicated shape such that a breakable upper portion is provided in the upper portion of a cylindrical section into which the shaft section of a fastener is inserted are connected using a bridge is also known (refer to Patent document 3).
Since fasteners are often driven continuously in actual processing, it is preferable that a connected fastener assembly should be configured so that a large quantity of fasteners can be loaded into a fastener driving tool at a time. In this respect, connected fastener assembly according to the wire connecting method for winding into a coil or the plastic sheet connecting method are used advantageously. However, in the case of the connected fastener assembly according to the wire connecting method, wires are scattered at the time of driving, whereby there is a danger of striking and injuring human bodies and garbage is produced. Furthermore, the shaft sections of the fasteners are welded to wires in this method. In the case that the fasteners are hardened nails, for example, the strength thereof is lowered at the welded portions by heat during welding. Therefore, when such nails are driven into high-strength concrete or the like, the nails are likely to buckle or fracture. Moreover, if the connected fastener assembly wound into a coil is dropped to the floor or ground inadvertently when the connected fastener assembly is loaded into the magazine of a fastener driving tool, the exterior of the coil may be deformed. If the exterior is deformed, it is difficult to restore the coil into its original shape. Besides, when the connected fastener assembly wound into a coil is carried, a finger is inserted into the center hollow portion of the coil. In this case, there is a danger that the finger is injured by the tip ends of the wires.
On the other hand, in the case of the connected fastener assembly according to the plastic sheet connecting method, each fastener is detached from the connecting band and driven at the time of driving. It is thus necessary to form an ejection hole for ejecting the connecting band remaining in the nose section of a fastener driving tool. Hence, the strength of the nose section lowers, and the connecting band becomes garbage and must be thrown away.
Furthermore, the connected fastener assembly obtained according to the method disclosed in Patent documents 6 and 4 in which fasteners are connected using a connecting sheet made of a synthetic resin is simple in structure. However, since the connecting band thereof is basically formed of a sheet material made of a synthetic resin, the strength of the ring-shaped retaining sections for allowing the shafts of the fasteners to be inserted is not very high. Hence, when the first fastener of the connected fastener assembly is fed into the injection section (the nose section) of a fastener driving tool and is impacted by its driver, the fastener may tilt inside the injection section. When this problem occurs, it is impossible for the ring-shaped retaining section to properly control the attitude of the fastener so that the fastener does not tilt.    [Patent document 1] Japanese Patent Application Laid-Open Publication No. 2003-301824    [Patent document 2] Japanese Patent Application Laid-Open Publication No. 2000-240622    [Patent document 3] Japanese Patent No. 2588812    [Patent document 4] Japanese Patent Application Laid-Open Publication No. Sho 57-120713    [Patent document 5] Japanese Utility Model No. 2526455    [Patent document 6] Japanese Patent Application Laid-Open Publication No. 2005-90723    [Patent document 7] Japanese Utility Model Application Laid-Open Publication No. Hei 6-35623
However, the above-mentioned connection methods have problems. For example, in the case of the connected fastener assembly according to the wire connecting method, since the distance between the two wires is fixed, fasteners having short shafts cannot be connected. Furthermore, since the wires are apt to be deformed relatively easily, there is a problem of shaft tangling in which the tip ends of the shafts of adjacent fasteners are tangled with one another.
Moreover, in the case of the connected fastener assembly according to the synthetic resin connection method, since the connecting band has a complicated shape, there is a problem in which the connecting band breaks due to impact repeatedly applied at the time of fastener driving.
Besides, even in the case of the connected fastener assembly according to the plastic sheet connecting method, since the distance between the upper and lower retaining pieces is constant, short fasteners cannot be connected.
Additionally, since the connecting means disclosed in Patent document 3 is complicated in shape as a whole and can be produced only by extrusion molding, there is a problem of high cost.
Still further, there are problems with respect to the connection configuration. In the case of a fastener driving tool equipped with a straight magazine, only straight-type connected fastener assemblies can be used, but coil-type connected fastener assemblies cannot be used. Conversely, in the case of a fastener driving tool equipped with a cylindrical magazine, only coil-type connected fastener assemblies can be used, but straight-type connected fastener assemblies cannot be used. Hence, connected fastener assemblies conforming to the type of a fastener driving tool to be used must be supplied thereto. As a result, since different types of connection facilities are required depending on the connection configuration of fasteners, the volume of production is dispersed, the operation rates of the connection facilities are reduced, and the production cost cannot be reduced.
In addition, in the case that the outside diameter of the shaft guide is the same as that of the ring-shaped retaining section, when a connected fastener assembly having this configuration is stored in a storage box or loaded into a fastener driving tool, the connected fastener assembly is wound into a coil as a whole and the coil is grasped and lifted by hand. At this time, a phenomenon may occur in which the center side portion of the coil cannot be held with the outer circumferential side portion thereof, and the center side portion drops due to its own weight. If this phenomenon of center side dropping occurs, the coil hangs down loosely as a whole, and the connected fastener assembly must be rewound. This rewinding is troublesome and takes a long work time.